'Dirty money' - how our banknotes are covered with pathogens

The phrase “dirty money” may have different meanings, but in terms of microbiology, a surprisingly high percentage of bank notes carry high numbers of pathogenic bacteria.

Handing over money or receiving change is a significant means of passing germs, according to a new study. Habip Gedik at the Okmeydani Training and Research Hospital in Istanbul, Turkey, and his colleagues in the Netherlands investigated how well bacteria survived on seven currencies: the euro, U.S. dollar, Canadian dollar, Moroccan dirham, Croatian kuna, Romanian leu and Indian rupee.

As part of their research, the team studied to what extent the euro, leu and U.S. dollar could spread E.coli or Staphylococcus aureus onto people's skin. They made volunteers with clean hands rub contaminated bills for 30 seconds and then tested their fingers for bugs. What they found was that people who handled euros coated in E.coli were bacteria-free, but those who handled the leu got both types of bacteria on their skin. People who handled US dollars laced with S. Aureus also got the bug on their fingers.

Interestingly the leu is made of polymer fibers. Polymer banknotes last longer and are harder to counterfeit than traditional cotton-fiber ones. Canada has already switched to this type of bank note and the U.K. is set to begin phasing 'plastic notes' in from 2016, according to The Independent.

The findings of the study have been published in the journal Antimicrobial Resistance & Infection Control, in a paper titled "Impact of universal screening on MRSA bacteremias in a single acute NHS organisation (2006–12): interrupted time-series analysis."

These findings support some conducted a year earlier. Independent tests on European money conducted by a team of scientists at Oxford University in December 2012 found that the average banknote contains 26,000 bacteria, enough germs to spread disease, according to CNN.

In another study, 97 percent of bank notes sampled tested positive for the presence of potentially dangerous bacteria on their surface: raising concerns over the spread of disease in places such as hospitals, according to the Irish Examiner.

Globally, money is one of the items most frequently passed from hand to hand. Perhaps a little care and attention is required? Perhaps. The level of contamination and type or organisms on the money will vary depending on the country, season, environmental conditions, type of money (paper vs coins), the type of material the money is made off, local community flora, the general hygiene level of the population and who is likely to be handling the money.